Chinese digger recommendations

[dfkrug]

the XIX has the 902 and it is 16 HP vs 14HP of the 722.

I love those 2 Kubota DI diesel engines, even made in China. But, both the D722 (719cc) and D902 (898cc) 3-cyl engines may be specced for those outputs, but that's at 3600RPM (crazy-fast).

I don't know if the engine speed controls on these minis even LET you go that fast. More likely, they run at 2000-2500 RPM. At 2000 RPM, they put out 9 and 12hp, respectively.

The Kubota K008 uses the D722, and it is rated at 10.2hp because it is run at about 2100-2200 RPM.

If the Typhon or other units with either engine go much faster, please tell.

 

[Carl_NH]

DF as usual you are correct! The 722 in my Typhoon maxes out at 2400 RPM but I generally run it at 1900 to 2000 as that seems to be the sweet spot for smooth operation and digging.

http://www.steam-brite.com/equipment/Kubota-D722-PC[1].gif

 

[TexTrctr]

From looking at the engine specs at the Kubota site, @3600 rpm the 902 is rated at 18.5kw(24.8hp)! My Typhon XIX manual lists the 902 with a rated power of 11.8kw (15.8hp)@2500rpm. The max torque is listed as 42.9nm@2000rpm. The Typhon data points don’t match the curves on the Kubota chart so I assume the minis are using a continuous duty-cycle rating. The curves Kubota supplies are an intermittent rating. Anyway, that torque translates to 9 kw(12hp) at that speed. I would expect that this might be a good speed setting for doing work with these things since, in a previous life, our HD on-highway diesels liked to operate at peak torque, which is usually close to best efficiency (lowest BSFC).

 

[D'oh]

Hydaulic Pump is the Key. It is not outright HP of the engine, it is what the Hydraulic Pump can produce at "X"RPM, and what power it takes to turn that pump at that speed. Oil Viscosity would also come into play.

Kind of why the mini Skid Steers with 12.5hp and 23hp Engines perform very simularly

 

[2manyrocks]

Ordinarily, I strongly prefer any diesel engine to a gas engine in a tractor. Don't really like the 20hp V twin gas engine in my Terramite backhoe for example. Seems to burn a lot of gas in a day.

Is a diesel really worth it to power these chinese mini excavators compared to the ones that have the small 13hp or so gas engines? I wouldn't think these smaller gas engines would burn much gas, but I'd think the little Kubota diesels would be highly fuel efficient and have excellent life time durability.

 

[Carl_NH]

Diesel is my preference, but its not all about the power plant - it's what's included in the diesel mini's. The small 1 ton gas don't get hyd cooling, have a single pump Then noise, heat, and gas use is higher.

The diesel has a bigger frame, heavier, longer tracks, run cooler etc,. Yes there is a cost but for the 5-6K more the diesel are worth it with the extra features included standard.

 

[dfkrug]

The Typhon data points don’t match the curves on the Kubota chart so I assume the minis are using a continuous duty-cycle rating. The curves Kubota supplies are an intermittent rating.

Good point. The hp numbers I quoted above are off a Kubota engine spec chart.

I have harped on this point, but it bears repeating: Any of the Diesels (1, 2, or 3-cyl) seem happiest to operate at about 2000-2200 RPM, and the makers have usually sized the pumps to work at that speed (6.8cc/rev for the single pumps).

Transplanting a gas engine (420-440cc thumper, or V-twin GX clone) really needs to have a smaller pump installed. These engines are happiest at about 3000RPM, or a little higher.

 

[2manyrocks]

Is pump size relative to gas engine RPM one of the reasons for some of the gas units being so jerky in operation?

 

[dfkrug]

Is pump size relative to gas engine RPM one of the reasons for some of the gas units being so jerky in operation?

Two reasons for jerkiness: Low weight, and flow rate too fast. Most gas 1-2T minis have too much flow at 3000 RPM, so reducing flow rate would help, yes.

Crappy valves without good "feathering ramps" could exacerbate jerkiness, but I have found (by taking them apart) that the valves are good quality in that area.

 

[TexTrctr]

Ok, I'm looking for an auger for the miniX that's supposed to be delivered tomorrow (I'd like to buy it before tariffs kick in). Problem is the dimensions at the attachment points are all over the map from the EBay/Alibaba/Aliexpress vendors. I thought the bracket opening was 90mm and the pin spacing was 90mm but I'm seeing those numbers +- 5mm. Maybe on the bracket opening, that's sorta ok, but the pin spacing has to be pretty exact. I'm guessing that all would probably work for a 1-1.8 ton excavator, but, geez, it shouldn't be that hard to have consistant numbers.
Any words of wisdom from you guys?
BTW, as a newbie, I really appreciate you folks as a resource.